The present invention relates to an improved device for carrying out stress tests on reconstituted materials taken from a geologic formation and to an implementing method.
A testing device adapted for exerting stresses on cylindric-shaped geologic samples is known through the published French Patent Application FR 2,633,718. It comprises a central body fitted with an axial cavity open at one end and closed at the other end. A tubular chamber made of a deformable material and connected with means for producing a fluid under pressure is arranged in this cavity. A cylindric-shaped sample is placed in the centre of the deformable chamber. The body is closed by elements forming a cover equipped with a central bore for a piston likely to rest against one end of the sample. Strain gages stick to the sample and are linked to the outside by conductors passing across the cover. The deformable chamber is fitted with tight radial passageways for several sensors adapted for measuring the lateral displacements of the sample. A fluid is injected in order to dilate the deformable chamber and to apply radial stresses to the sample. At the same time, a considerable axial force is applied to the piston by means of a jack for example, and the deformations and the displacements undergone by the sample are recorded.
This device is suited for examining substantially cylindric-shaped samples subjected to radial and axial stresses at the same time and the data that are produced are those which are measured by sensors actually placed in contact with the tested sample. The improved device according to the invention has been developped in order to facilitate and speed up the setting of samples to be subjected to stresses following several directions, and also in order to analyze in a more subtle way the behaviour of the samples during the tests.